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| 1676 | tullio | 1 | %---------------------------------------------------------------------------- |
| 2 | \chapter{The CMOS real-time clock} |
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| 3 | %---------------------------------------------------------------------------- |
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| 4 | |||
| 5 | In all PCs there is a real-time clock (with a resolution of 1 second) that can |
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| 6 | be read or written. This clock usually has a drift of about some seconds in 24 |
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| 7 | hours. The following functions (that can be found into \texttt{rtc.h}) can be |
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| 8 | used to set/get values; all values are passed using a \texttt{struct rtc\_time} |
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| 9 | that contains variables for seconds, minutes, hours, days, months and years. |
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| 10 | |||
| 11 | \vspace{7mm} |
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| 12 | |||
| 13 | \begin{intest} |
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| 14 | GET\_RTC\_TIME\index{get\_rtc\_time()} |
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| 15 | \end{intest} |
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| 16 | |||
| 17 | \begin{description} |
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| 18 | \item [\textbf{int get\_rtc\_time(struct rtc\_time {*}time);}] |
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| 19 | \item [\textbf{Description:}] The actual time is read from the CMOS real-time clock and |
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| 20 | written into the structure pointed by \texttt{time}. The function returns zero |
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| 21 | on success, other values on error. |
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| 22 | \end{description} |
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| 23 | |||
| 24 | \begin{intest} |
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| 25 | SET\_RTC\_TIME\index{set\_rtc\_time()} |
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| 26 | \end{intest} |
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| 27 | |||
| 28 | \begin{description} |
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| 29 | \item [\textbf{int set\_rtc\_time(struct rtc\_time {*}time);}] |
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| 30 | \item [\textbf{Description:}] The values contained in the structure pointed by |
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| 31 | \texttt{time} are converted in seconds and written into the CMOS real-time |
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| 32 | clock; the function returns zero on success, other values on error. |
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| 33 | \end{description} |
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| 34 | |||
| 35 | \begin{intest} |
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| 36 | RTC\_TIME\index{RTC\_TIME, structure} |
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| 37 | \end{intest} |
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| 38 | |||
| 39 | \begin{description} |
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| 40 | \item [\textbf{Description:}] it is a data structure containing the following fields:\\ |
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| 41 | \textbf{tm\_sec} : seconds, from 0 to 59;\\ |
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| 42 | \textbf{tm\_min}: minutes, from 0 to 59;\\ |
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| 43 | \textbf{tm\_hour}: hours, from 0 to 23;\\ |
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| 44 | \textbf{tm\_mday} : day, from 1 to 31;\\ |
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| 45 | \textbf{tm\_mon} : month, from 1 to 12;\\ |
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| 46 | \textbf{tm\_year} : year, is an integer number (no Y2K problem);\\ |
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| 47 | \textbf{tm\_wday} : day of the week, from 1 to 7;\\ |
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| 48 | \textbf{tm\_yday} : day of the year, from 1 to 365;\\ |
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| 49 | \textbf{tm\_isdst} : 0 if legal hour, 1 if solar hour (not used yet);\\ |
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| 50 | \end{description} |